Laboratory vacuum induction heats of 18%-Ni mar aging steels were cast into 25-pound ingots and forged into flat bar stock. Transverse tensile and Charpy V specimens were obtained from the forged material. One composition contained 8.4% Co, 3.2% Mo, and 0.2% Ti; five others contained 7% or 9% Co and 3.2%, 3.8%, or 5% Mo, but no titanium. Specimens were aged at various tempera tures up to 1000 F, and Charpy V and tensile properties were determined at room temperature. Charpy V tests were also conducted at 30 and -20 F. The titanium- containing composition con sistently developed considerably better combina tions of Charpy V toughness and yield strength than did the others.

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